1. Field of the Invention
The present invention relates generally to a probe for monitoring reflux of hydrochloric acid from the stomach into the esophagus, a condition known as gastroesophageal reflux disease. More particularly, the present invention is directed to a bifurcated, adjustable, multiple, internal reference probe for detecting acid reflux and monitoring pH levels of acid reflux episodes simultaneously at multiple locations within the pharyngoesophageal passage.
2. Description of the Related Art
Gastroesophageal reflux disease (GERD), often referred to as “reflux esophagitis”, is a prevalent and ongoing problem for a significant number of people within the pediatric and adult populations of the United States and other countries, and a variety of otolaryngological abnormalities have been attributed to contact of gastroesophageal refluxate with respective structures of the aerodigestive tract. GERD is a condition in which stomach acids surge upward or reflux from the stomach into the esophagus. These acids may cause serious problems, including harsh burning sensations in the throat, chest, and neck, regurgitation, inhalation of refluxed material leading to aspiration pneumonia, swallowing difficulties, i.e., dysphagia, ulcerations of the esophageal lining, and esophageal cancer. GERD is generally caused by failure of a thickened area in the muscular wall (sphincter) of the lower esophagus that acts as a one-way valve between the stomach and esophagus, i.e., the GE junction, to properly close after swallowed liquid and solids are passed into the stomach. This valve is a high pressure zone of the esophagus (e.g., between 15 and 30 mm Hg pressure) called the lower esophageal sphincter (LES). The failure or ineffectiveness of the LES may be caused by a number of physical problems, such as by decreased resting tone in the ring-like, smooth-muscle layer of the LES, or by a hiatal hernia, which is an opening in the diaphragm, i.e., the hiatus, that is larger than necessary for the esophagus to pass into the abdominal cavity. A common cause of GERD is inappropriate muscular relaxation of a person's LES, even though the LES may have a normal resting pressure.
A second sphincter, called the upper esophageal sphincter (UES), is located approximately 25 cm above the LES and separates the esophagus from the pharynx. A primary function of the UES in the human body is to prevent the passage of inadvertently swallowed objects, such as fish bones, into the esophagus, although it is also implicated in controlling effects of gastroesophageal reflux. For example, gastroesophageal refluxate that gets past the UES and into the pharynx above the UES has been associated with vocal cord contact ulcer and a variety of other otolaryngological systems and disorders ranging from chronic hoarseness and laryngitis to laryngospasm, and otitis media have been attributed to contact of gastroesophageal refluxate with respective structures of the aerodigestive tract, such as subglottal strictures, and a variety of other laryngeal and head and neck abnormalities. See, e.g., R. Shaker et al., “Esophageal Distribution of Refluxed Gastric Acid in Patients with Reflux Laryngitis,” Gastroenology, Vol. 109, pages 1575–82 (1995), hereby incorporated by reference.
In order to determine a proper course of treatment for a patient suffering from such abnormalities, it is helpful to know whether GERD may be an underlying cause and should be a target in the treatment. If the person has GERD, it is desirable to be able to accurately monitor gastric acid reflux episodes to determine their severity, frequency, and also whether they coincide with other events, such as eating meals, sleeping, or belching. Devices for sensing pH levels in the esophagus may include one or multiple pH sensors, such as antimony (Sb) billets, and conductive wires enclosed in a protective housing, such as a flexible plastic tube, that can be inserted into the patient's esophagus and connected to a recorder or logger outside the patient's body, where the recorder receives and records voltages from the antimony sensor(s) that are indicative of changes in pH levels, i.e., acidity, over time. The sensor(s) in the tube are generally inserted into a patient intranasally, fed downwardly through the pharynx, and into the patient's esophageal passage until the sensor(s) reaches the location(s) where it is desired to acquire the pH readings. Such multiple antimony pH sensors in a tube for insertion into the esophagus and ambulatory pH records for monitoring and recording gastroesophageal refluxate are commercially available, such as the ComforTECH (trademark) pH catheters and Biostar (trademark) recorders made by Sandhill Scientific, Highlands Ranch, Colo., USA. Other sources may include Del Mar Avionics of Ervin, Calif., and Synectics Medical, Inc., Irving, Tex.
However, for monitoring of gastroesophageal retluxate in patient-specific diagnostics of such otolaryngological symptoms and disorders as those described above, as well as in group studies of gastroesophageal refluxate effects, it is often desirable to have the antimony sensors positioned in specific locations in the pharynx (above the UES), proximal esophagus (below the UES), and distal esophagus (above the LES). For example, a physician might want a first antimony sensor positioned in the distal esophagus a specific distance, such as about 5 cm above the LES to detect and monitor when refluxate gets through the LES and into the distal esophagus, how acidic it is, and how long it remains in the distal esophagus before it clears. At the same time, the physician may want to also position a second antimony pH sensor a specific distance, such as about 3 cm, below the UES to detect and monitor when such refluxate gets all the way up to the proximal esophagus just under the UES, how acidic it is, and how long it remains in the proximal esophagus before it clears. It may be useful to also position even a third antimony pH sensor a specific distance, such as about 2 cm, above the UES to detect and monitor whether refluxate gets through the UES and into the pharynx, and, if so, how acidic it is, and how long it remains in the pharynx before it clears. However, the length of the esophagus, i.e., the distance between the LBS and the UES, varies from person to person, so conventional probes or catheters with multiple pH sensors do not meet this requirement. Therefore, a need may have previously existed and may have been identified by those in the relevant fields as a deficiency in heretofore previous systems. A previous attempt described in the Shaker et al. article cited above may have addressed the issue by using two separate probes with two separate recorders simultaneously, a single-site pH probe and recorder made by Del Mar Avionics, Ervin, Calif., and a dual-site pH probe and recorder made by Synectics Medical, Inc., Irving, Tex., and then correlating the data from both probes.
The described method of Shaker et al., however, may be unsatisfactory for clinical use by doctors, nurses, and patients who do not have the time, training, or patience to calibrate, install, monitor, and correlate data from two separate probes and recorders.